dynamodb QueryRequest & ScanRequest

public void addUser(String id, Date date) {

    Map<String,AttributeValue> attributeValues = new HashMap<>();
    attributeValues.put("id",new AttributeValue().withS(id));
    attributeValues.put("timestamp",new AttributeValue().withN(Long.toString(date.getTime())));

    PutItemRequest putItemRequest = new PutItemRequest()
        .withTableName(TABLE_NAME)
        .withItem(attributeValues);

    PutItemResult putItemResult = dynamoDB.putItem(putItemRequest);
  }

  public Integer countUsers(String id) {
    List<Map<String,AttributeValue>> items = new ArrayList<>();

    Map<String,String> expressionAttributesNames = new HashMap<>();
    expressionAttributesNames.put("#id","id");

    Map<String,AttributeValue> expressionAttributeValues = new HashMap<>();
    expressionAttributeValues.put(":idValue",new AttributeValue().withS(id));

    QueryRequest queryRequest = new QueryRequest()
        .withTableName(TABLE_NAME)
        .withKeyConditionExpression("#id = :idValue")
        .withExpressionAttributeNames(expressionAttributesNames)
        .withExpressionAttributeValues(expressionAttributeValues)
        .withSelect(Select.COUNT);

    Map<String,AttributeValue> lastKey = null;
    QueryResult queryResult = dynamoDB.query(queryRequest);
    List<Map<String,AttributeValue>> results = queryResult.getItems();
    return queryResult.getCount();
  }

  public List<Map<String,AttributeValue>> fetchUsersDesc(String id) {

    List<Map<String,AttributeValue>> items = new ArrayList<>();

    Map<String,String> expressionAttributesNames = new HashMap<>();
    expressionAttributesNames.put("#id","id");

    Map<String,AttributeValue> expressionAttributeValues = new HashMap<>();
    expressionAttributeValues.put(":idValue",new AttributeValue().withS(id));

    QueryRequest queryRequest = new QueryRequest()
        .withTableName(TABLE_NAME)
        .withKeyConditionExpression("#id = :idValue")
        .withExpressionAttributeNames(expressionAttributesNames)
        .withExpressionAttributeValues(expressionAttributeValues)
        .withScanIndexForward(false);

    Map<String,AttributeValue> lastKey = null;

    do {

      QueryResult queryResult = dynamoDB.query(queryRequest);
      List<Map<String,AttributeValue>> results = queryResult.getItems();
      items.addAll(results);
      lastKey = queryResult.getLastEvaluatedKey();
      queryRequest.withExclusiveStartKey(lastKey);
    } while (lastKey!=null);

    return items;
  }

  public List<Map<String ,AttributeValue>> queryUsersBetween(String id, Date from, Date to) {

    List<Map<String,AttributeValue>> items = new ArrayList<>();

    Map<String,String> expressionAttributesNames = new HashMap<>();
    expressionAttributesNames.put("#id","id");
    expressionAttributesNames.put("#timestamp","timestamp");

    Map<String,AttributeValue> expressionAttributeValues = new HashMap<>();
    expressionAttributeValues.put(":idValue",new AttributeValue().withS(id));
    expressionAttributeValues.put(":from",new AttributeValue().withN(Long.toString(from.getTime())));
    expressionAttributeValues.put(":to",new AttributeValue().withN(Long.toString(to.getTime())));

    QueryRequest queryRequest = new QueryRequest()
        .withTableName(TABLE_NAME)
        .withKeyConditionExpression("#id = :idValue and #timestamp BETWEEN :from AND :to ")
        .withExpressionAttributeNames(expressionAttributesNames)
        .withExpressionAttributeValues(expressionAttributeValues);

    Map<String,AttributeValue> lastKey = null;

    do {

      QueryResult queryResult = dynamoDB.query(queryRequest);
      List<Map<String,AttributeValue>> results = queryResult.getItems();
      items.addAll(results);
      lastKey = queryResult.getLastEvaluatedKey();
      queryRequest.setExclusiveStartKey(lastKey);
    } while (lastKey!=null);

    return items;
  }

  public List<String> scanUsers(Date date) {

    List<String> ids = new ArrayList<>();


    Map<String, String> attributeNames = new HashMap<String, String >();
    attributeNames.put("#timestamp", "timestamp");


    Map<String, AttributeValue> attributeValues = new HashMap<String, AttributeValue>();
    attributeValues.put(":from", new AttributeValue().withN(Long.toString(date.getTime())));


    ScanRequest scanRequest = new ScanRequest()
        .withTableName(TABLE_NAME)
        .withFilterExpression("#timestamp < :from")
        .withExpressionAttributeNames(attributeNames)
        .withExpressionAttributeValues(attributeValues)
        .withProjectionExpression("id");

    Map<String,AttributeValue> lastKey = null;

    do {

      ScanResult scanResult = dynamoDB.scan(scanRequest);

      List<Map<String,AttributeValue>> results = scanResult.getItems();
      results.forEach(r->ids.add(r.get("id").getS()));
      lastKey = scanResult.getLastEvaluatedKey();
      scanRequest.setExclusiveStartKey(lastKey);
    } while (lastKey!=null);

    return ids;
  }